Compared with non-auxetic materials, auxetic materials have special and desirable mechanical properties. For example, if the material has a crack, when it is being pulled apart, it expands and closes up the crack. In other words, this type of material has more crack resistance to fracture. Also, it has high material resistance to shear strain. Shear resistance is particularly important in structural components such as sheets or beams in buildings, cars and aircraft. In the present paper strain energy density, temperature variation, thermal stresses and total stresses in an infinite plate of auxetic material with a line crack, subjected to the mechanical and thermal loading in the context of thermo elastic theory are studied. Key words: Auxetic behavior, thermal stresses, strain energy function, temperature variation.